Hidrogélek kölcsönhatása biológiai szempontból jelentős vegyületekkel = Interaction of hydrogels with biologically relevant species in aqueous phase

Az orvosbiológiai és elválasztástechnikai célokra is elterjedten használt reszponzív polimer alapú rendszerekben az anyagfelvételt és -leadást irányító kölcsönhatásokat még mindig nem ismerjük pontosan. Térhálós poli-N-izopropil-akrilamid (PNIPA) hidrogélek fázisátalakulási tulajdonságait különböző biológiailag releváns ionok, aromás molekulák, aminosavak és protein jelenlétében vizsgálva megállapítottuk, hogy hatásuk nemcsak az oldószer ’jóságának’ módosítására vezethető vissza, hanem anyagi minőségüktől függően speciális kölcsönhatás(oka)t alakíthatnak ki a PNIPA oldalláncával. A kölcsönhatásokat befolyásoló tényezők feltérképezésére komplex megközelítést alkalmaztunk (mikrokalorimetria, NMR, szórási módszerek, duzzadási vizsgálatok, mechanikai tulajdonságok, porozitás, stb.). Az irodalomban elsőként publikáltuk a kölcsönható egységek lehetséges konformációit és az atomi távolságokat. Hidrofób módosításokkal kísérletet tettünk a PNIPA gél több tulajdonságának (mechanikai, szorpciós) javítására. A hőmérsékletérzékeny NIPA származékok mellett pH- és redox-érzékeny poli(aszparaginsav) (PASP) géleket is vizsgáltunk. Kettős reszponzív tulajdonságuk, magas víztartalmuk és mechanikai stabilitásuk orvosbiológiai alkalmazásokban előnyös lehet. Kriogén körülmények között NIPA és PASP alapú szupermikropórusos géleket állítottunk elő. Ezek gyors kinetikájuknak köszönhetően igen ígéretesek a célzott és programozott hatóanyagleadásban. | The majority of thermosensitive gels used in biotechnological applications are either homopolymers or co-polymers of N-isopropylacrylamide (NIPA). These applications are based on the ability of PNIPA hydrogels to adsorb, retain and separate different target molecules. The still poorly understood nature of the interactions with small molecules is a vital indicator in understanding a wide variety of systems of biomedical interest. Our observations based on high-resolution DSC, SANS and solid-state NMR converge to show that small aromatic molecules (SAMs) interact with PNIPA hydrogels not only by altering the average solvent quality of the diluent, but also by specific association with the side-chain groups in the NIPA subunits. The effect is strongly influenced by the substituent(s) of the aromatic ring. The most probable conformations and the interactions on atomic level were specified the first time. The potential improvement of the sorption and mechanic properties of PNIPA by hydrophobic modifications was studied. pH and redox responsive poli(aspartic acid) (PASP) gels were also investigated. Their stimuli sensitive properties along with their high water content and good mechanical stability make disulfide cross-linked PASP hydrogels good candidates for human biological applications. NIPA and PASP based supermacroporous polymers were synthesized also in cryogenic conditions. Due to the fast kinetics they are promising vectors for targeted and time controlled drug delivery

Felületkémia és szelektivitás nagyfelületű szeneken = Chemical structure and performance of high surface area carbons

A hamumentes polimer alapú szeneken vizsgáltuk a felületkémia és a szorpciós tulajdonságok közti kapcsolatot. Morfológiailag igen hasonló, vízmentes és vizes közegben jellemzett oxigén, nitrogén és hidrogén heteroatomot tartalmazó szeneken mind gőz-, mind hígoldat adszorpciós folyamatokban igazoltuk a felület kémiai tulajdonságainak meghatározó jellegét. A felületi tulajdonságok nem csak az egyensúlyt, de a folyamatok sebességét is befolyásolják. Új függvényt vezettünk be a póruskitöltődés nyomonkövetésére és ennek használhatóságát mind poláros, mind apoláros gőzök esetén bemutattuk. Vizsgáltuk további, elsősorban fém heteroatomok beviteli lehetőségeit polimer alapú szénmátrix kialakításának különböző stádiumaiban. Megállapítottuk, hogy lignocellulóz alapú szenek esetében a Na és Si atomok bevitele (vízüveges módosítás) gyakorlatilag nem befolyásolja a vizsgált szorpciós tulajdonságokat, de kedvezően hat a mechanikai tulajdonságokra. Amennyiben a fémionok hozzáadása a prekurzor polimer szintézise során ill. a pórusos szerkezet rögzítése (szárítás) előtt történik, a mátrix szerkezete, a fajlagos felület és a pórusszerkezet is jelentősen módosul. Utólagos kezelés esetén a porozitáshoz kapcsolható változásokat elsősorban a pórusok eltömődése okozza. | The relationship between surface chemistry and sorption performance was studied on ash-free polymer-based carbons. In carbons that were morphologically similar and contained oxygen, nitrogen and hydrogen hetero atoms, the role of the surface chemistry was demonstrated in sorption processes from both the vapour and the liquid phase. The surface properties influence not only the adsorption equilibrium but play a role in the kinetics as well. A new function was introduced to follow the pore filling. Its applicability was shown for polar and nonpolar vapours. The possibility of introducing further, mainly metal, heteroatoms was studied at various stages of the carbon synthesis. In the case of lignocellulosic matrices we found that introducing Si and Na atoms (in the form of waterglass) results in improvement of mechanical strength rather than of the adsorption properties. When metal ions were added to the polymer precursor during the polymerization step or before the drying process, both the morphology and the porosity of the matrix can be severely influenced. Post-carbonization treatment, however, leads to obstruction of the pore entrance and thus a reduction of the accessible porosity

Hydrothermal Synthesis and Gas Sensing of Monoclinic MoO3 Nanosheets

Effects of different reaction parameters in the hydrothermal synthesis of molybdenum oxides (MoO3) were investigated and monoclinic (β-) MoO3 was prepared hydrothermally for the first time. Various temperatures (90/210 °C, and as a novelty 240 °C) and durations (3/6 h) were used. At 240 °C, cetyltrimethylammonium bromide (CTAB) and CrCl3 additives were also tested. Both the reaction temperatures and durations played a significant role in the formation of the products. At 90 °C, h-MoO3 was obtained, while at 240 °C the orthorhombic (α-) MoO3 formed with hexagonal rod-like and nanofibrous morphology, respectively. The phase transformation between these two phases was observed at 210 °C. At this temperature, the 3 h reaction time resulted in the mixture of h- and α-MoO3, but 6 h led to pure α-MoO3. With CTAB the product was bare o-MoO3, however, when CrCl3 was applied, pure metastable m-MoO3 formed with the well-crystallized nanosheet morphology. The gas sensing of the MoO3 polymorphs was tested to H2, which was the first such gas sensing study in the case of m-WO3. Monoclinic MoO3 was found to be more sensitive in H2 sensing than o-MoO3. This initial gas sensing study indicates that m-MoO3 has promising gas sensing properties and this MoO3 polymorph is promising to be studied in detail in the future

Preparation and characterization of a nitrogen-doped mesoporous carbon aerogel and its polymer precursor

Nitrogen-containing carbon aerogel was prepared from resorcinol–melamine–formaldehyde (R–M–F) polymer gel precursor. The polymer gel was supercritically dried with CO2, and the carbonization of the resulting polymer aerogel under nitrogen atmosphere at 900 °C yielded the carbon aerogel. The polymer and carbon aerogels were characterized with TG/DTA–MS, low-temperature nitrogen adsorption/desorption (− 196 °C), FTIR, Raman, powder XRD and SEM–EDX techniques. The thermal decomposition of the polymer aerogel had two major steps. The first step was at 150 °C, where the unreacted monomers and the residual solvent were released, and the second one at 300 °C, where the species belonging to the polymer network decomposition could be detected. The pyrolytic conversion of the polymer aerogel was successful, as 0.89 at.% nitrogen was retained in the carbon matrix. The nitrogen-doped carbon aerogel was amorphous and possessed a hierarchical porous structure. It had a significant specific surface area (890 m2 g−1) and pore volume (4.7 cm3 g−1). TG/DTA–MS measurement revealed that during storage in ambient conditions surface functional groups formed, which were released upon annealing

Role of water molecules in the decomposition of HKUST-1: Evidence from adsorption, thermoanalytical, X-ray and neutron scattering measurements

HKUST-1 is a strictly microporous crystalline metal organic framework with pore sizes of 5, 11, and 13.5 Å. Detailed gas adsorption measurements show that its adsorption capacity for water at 20 °C is higher than that for nitrogen at-196 °C, and far exceeds that for methane at 0 °C. Extended exposure to water vapour at high relative humidity, or consecutive adsorption-desorption cycling of water vapour, destroys both the MOF crystal structure and its adsorption capacity, after a reduced number (< 5) of cycles. Destruction proceeds through mesoporous defects that open within the crystal structure, as attested both by the development of hysteresis in the adsorption isotherms and by changes in the small angle X-ray scattering pattern. In the pristine crystal, the structure of the water in the micropores closely resembles that of bulk liquid water. Small angle neutron scattering demonstrates that water is adsorbed preferentially over methane, and that the size of the spherical cavities occupied by the adsorbed water molecules in the intact crystal is consistent with the known pore size structure in this system